Re: port forwarding in a web server

[Jeffrey Laramie <JALaramie@Loudoun-Fairfax.com>]

Juan Hernandez wrote:

>Hi there...
>
>   This may have been answered many times in this mailing list but I
>haven't found anything on the web about something that would make my
>server forward the way I want to, and what's ironic is that it seems
>simple. Here's my scenario: I have a static IP address routed (1.1.1.1)
>to one server using a 192.168.0.* address. Is a cisco router and
>everything works fine. This server has 192.168.0.1 as it's address and
>functions as a web server, everything works fine but, I have another
>server that works as our mail server that is using 192.168.0.2. I've
>been trying to redirect everything coming from port 25 to my mail server
>but it doesn't get any answer. These are the rules I've been using: 
>
>echo 1 > /proc/sys/net/ipv4/ip_forward
>
>modprobe iptable_nat
>
>#allow all outgoing traffic from the mail server 
>
>iptables -t nat -A POSTROUTING -p tcp -o eth0 -j SNAT --to 192.168.0.1
>
>#dnat
>iptables -t nat -A PREROUTING -p tcp --dport 25 -i eth0 -j DNAT --to
>192.168.0.1:25
>
>The gateway on the mailserver is 192.168.0.1 which is the webserver that
>it's forwarding everything... and I have tried so many things that
>sometimes the webserver stops working...
>  
>

I'm having trouble understanding questions this morning (maybe I need 
more coffee!). Is this your configuration?

router   <->   [firewall box]   <->   [webserver]   <->   [mailserver]

This won't work since the webserver doesn't know what to do with the 
packets your sending it on port 25. You need to direct the packets to 
192.168.0.2 port 25. If the mailserver is on a different LAN then you 
should be using a different subnet for each LAN. You'll also have to 
configure the mailserver to forward packets.

Hope this helps

Jeff